Influence of extra- and intra-oral application of CPP-ACP and fluoride on re-hardening of eroded enamel

The role of calcium in the prevention of erosive tooth wear: a systematic review and meta-analysis

OBJECTIVES

The loss of hard dental tissue due to recurrent acid challenges and mechanical stresses without bacterial involvement is known as erosive tooth wear (ETW). Many studies in the literature have concentrated on variables that may affect the ETW process and prevent its occurrence or reduce its advancement. However, to date, no previous systematic review has evaluated the role of calcium in preventing ETW. Therefore, the purpose of the present systematic review was to review and critically appraise the scientific evidence regarding the role of calcium formulations in the prevention of ETW.

METHODS

The review protocol was registered in the PROSPERO international prospective register of systematic reviews (Ref: CRD42021229819). A literature search was conducted in electronic databases to identify in situ randomized controlled trials evaluating the prevention of ETW following the application of calcium formulations. The outcomes studied included mean enamel loss, surface microhardness, surface roughness, mean erosion/softening depth, mineral loss/precipitation and remineralization. Study characteristics and outcomes of included studies were summarized. Cochrane's risk-of-bias tool 2.0 was used to assess the quality of eligible studies, and meta-analysis using a random effects model was performed.

RESULTS

The search retrieved 869 studies of which 21 were considered eligible. Regarding the results of the quality assessment for potential risk of bias in all included studies, overall, 5 studies were considered as being at low risk, another 12 at unclear risk and 4 at high risk of bias. The findings of the studies showed that the addition of calcium in juice drinks led to reduced enamel loss, with blackcurrant juice presenting 2.6 times statistically significant less enamel loss compared to orange juice (p = 0.0001, I2 = 89%). No statistically significant difference in mean surface microhardness of eroded enamel was recorded between chewing gum with or without casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (p = 0.31, I2 = 71%). Contradictory were the results regarding the effect of milk and CPP-ACP pastes on prevention of ETW.

CONCLUSIONS

Calcium formulations play an important role in ETW prevention, mainly through their addition to acidic drinks.

In situ effect of CO2 laser (9.3 μm) irradiation, combined with AmF/NaF/SnCl2 solution in prevention and control of erosive tooth wear in human enamel

OBJECTIVES

This single-blind, controlled cross-over in situ study aimed to evaluate the effect of CO2 laser (9.3µm) irradiation, combined with AmF/NaF/SnCl2 solution on prevention and control of Erosive Tooth Wear (ETW) in human enamel.

MATERIALS AND METHODS

Two trial conditions were analyzed, Condition-1 as ETW-prevention (sound tooth surface) and Condition-2 as ETW-control (in vitro initial erosive lesion). The experiment was conducted in two phases, one with one without exposure to AmF/NaF/SnCl2 solution. A hundred and ninety-two samples of human enamel (3x3x1mm) were randomly divided into 4 experimental groups for each condition: (C) without treatment (negative control); (F) AmF/NaF/SnCl2 solution (positive control); (L) CO2 laser irradiation; (L+F) CO2 laser+AmF/NaF/SnCl2 solution. Twelve volunteers used a removable device each containing 8 samples per phase. Ex-vivo erosive challenges (4×5min/day) and rinsing protocol (1×30s/day) were performed. The surface loss was determined using optical profilometer (n=12 per group), and the surface morphology was observed with Scanning Electron Microscopy (n=3).

RESULTS

Condition-1 data were analyzed by one-way ANOVA and Condition-2 by two-way repeated measures ANOVA, both with Tukey post-hoc tests (α=5%). Condition-1: groups L (4.59 ±2.95µm) and L+F (1.58 ±1.24µm) showed significantly less surface loss in preventing ETW than groups C and F. Condition-2: in controlling the progression of ETW, L+F was the only group with no significant surface loss between initial erosive lesion (3.65 ±0.16µm) and after erosive challenge (4.99 ±1.17µm).

CONCLUSIONS

CO2 9.3µm laser application prevented and controlled ETW progression in human enamel, with greater efficiency when combined with AmF/NaF/SnCl2 solution application.

The Effects of Three Remineralizing Agents on the Microhardness and Chemical Composition of Demineralized Enamel

This study aimed to determine the effects of three different varnish materials (containing casein phosphopeptide-amorphous calcium phosphate, nano-hydroxyapatite, and fluoride) on enamel. Thirty-three extracted human third molars were used for specimen preparation. These were demineralized using phosphoric acid. Three experimental groups (n = 11) were treated with 3M™ Clinpro™ White Varnish, MI Varnish^®, and Megasonex^® toothpaste, respectively, every twenty-four hours for fourteen days. Analysis of the microhardness of the specimens’ enamel surfaces was carried out via the Vickers method, and by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis was performed at three stages: at baseline value, after demineralization, and after the period of remineralization. Data were subjected to Scheffe’s post hoc test. The mean microhardness values (HV0.1) obtained for the group of samples treated with MI Varnish^® were higher compared with the other two groups (p = 0.001 for both comparisons), while the first and third groups did not differ significantly from each other (p = 0.97). SEM analysis showed uneven patterns and porosities on all samples tested. EDS results showed an increase in the mineral content of the examined samples, with the highest mineral content observed in the MI Varnish^® group. It can be concluded that MI Varnish^® use has a better remineralization effect on enamel than the other two materials.

The Addition of Propylene Glycol Alginate to a Fluoride Solution to Control Enamel Wear: An in situ Study

The aim of this study was to evaluate the protective effect of propylene glycol alginate (PGA) associated with sodium fluoride (NaF) against enamel erosion and erosion-abrasion. A 4-phase, split-mouth, double-blind, crossover in situ trial was conducted with the following solutions: F + PGA (225 ppm F- + 0.1% PGA), F (225 ppm F-), F + Sn (225 ppm F- + SnCl2, 800 ppm Sn2+), and negative control (distilled water). In each phase, 12 subjects wore removable mandibular appliances containing 4 enamel specimens, which were submitted either to erosion or to erosion-abrasion challenges for 5 days. Acquired salivary pellicle was formed in situ for 2 h. Erosion-abrasion consisted of acid challenge (1% citric acid solution, pH 2.3, 5 min, 4×/day), exposure to saliva in situ (2 h, 4×/day), brushing (5 s, total 2 min exposure to the slurry), and treatment with the solutions (2 min, 2×/day). For erosion, the same procedures were performed, without brushing. At the end, surface loss (SL; in μm) was evaluated by means of optical profilometry. KOH-soluble fluoride was quantified for erosion-only groups using extra specimens. For both challenges, the SL values found for F + PGA did not differ significantly from those of F and the negative control, and the SL value shown for F + Sn was significantly the lowest. Erosion-abrasion promoted significantly higher SL values than erosion. KOH-soluble fluoride analysis showed that F + Sn had a higher fluoride concentration in comparison with the negative control and F, while F + PGA did not differ from any of the other groups. In conclusion, PGA was not able to improve the protective effect of NaF against erosive enamel wear.

Effects of Additional Use of Bioactive Glasses or a Hydroxyapatite Toothpaste on Remineralization of Artificial Lesions in vitro

OBJECTIVES

This in vitro study aimed to evaluate and compare the effect of two different bioactive glasses, a hydroxyapatite-containing, fluoride-free toothpaste (HTP) and a fluoride toothpaste (FTP) on the remineralization behavior of initial caries lesions.

MATERIALS AND METHODS

A total of 100 bovine enamel samples were randomly allocated to five groups of 20 samples each: NC = negative control group (artificial saliva); HTP = HTP group (Karex); FTP = FTP group (Elmex caries protection, 1,400 ppm); FTP + BGnano = FTP followed by Actimins bioactive glass; FTP + BGamorph = FTP followed by Schott bioactive glass. Radiographic documentation (advanced transversal microradiography; aTMR) was applied before and after all samples were exposed to a demineralizing gel for 10 days. Over a period of 28 days, samples were covered twice a day (every 12 h) with a toothpaste slurry of the respective test group or with artificial saliva in NC for 60 s and brushed with 15 brushing strokes. Samples in FTP + BGnano and FTP + BGamorph were additionally treated with the respective bioactive glass slurry for 30 s after brushing with the FTP. In the meantime, all samples were stored in artificial saliva. After 28 days, the structure of all samples was assessed again using aTMR and compared to the values measured after demineralization. The statistical evaluation of the integrated mineral loss was performed using Kruskal-Wallis test followed by a post hoc Conover test.

RESULTS

The FTP revealed the significantly highest increase of mineral content while the HTP showed the significantly lowest remineralization. Compared to artificial saliva, the use of the HTP or the combined application of FTP followed by bioactive glasses (FTP + BGnano and FTP + BGamorph) showed no significant remineralization.

CONCLUSION

Under remineralizing in vitro conditions, brushing with 1,400 ppm FTP induced significantly more remineralization compared to storage in artificial saliva. The additional administration of both bioactive glasses as well as the substitutional brushing with an HTP resulted in significantly less remineralization compared to brushing with 1,400 ppm FTP.

In vitro and in vivo evaluation of electrophoresis-aided casein phosphopeptide-amorphous calcium phosphate remineralisation system on pH-cycling and acid-etching demineralised enamel

Casein phosphate-amorphous calcium phosphate (CPP-ACP), as a remineralisation agent, is extensively used in managing demineralised enamel; however, its remineralisation kinetics is low. This study aimed to improve remineralisation kinetics of CPP-ACP by introducing a rapid remineralisation method with electrophoresis. In vitro, a pH-cycling enamel model was used to test remineralisation potentials of electrophoresis-aided CPP-ACP. For verifying remineralisation potentials of electrophoresis-aided CPP-ACP in vivo in a rabbit model, acid-etched enamel surface on rabbit maxillary incisors was remineralised by electrophoresis-aided CPP-ACP with 1.0 mA (group A) or 0.5 mA (group B). Both in vitro and in vivo, it was observed that electrophoresis was benefit to improve remineralisation kinetics of CPP-ACP, and the demineralised enamel was completely remineralised after 5 h. The Ca/P ratio in remineralised enamel consisted with that of hydroxyapatite, the microstructure in native enamel. Meanwhile, in vivo the micro-hardness of acid-etched enamel in group A (322.55 ± 31.90) and group B (322.55 ± 31.90) recovered up to the value of native enamel after 5 h remineralisation (p > 0.05). The Hematoxylin-eosin stain demonstrated that the electric field used in this study was safe on rabbit dental pulp. Therefore, this efficient and safe method has the potential to be applied in treating enamel deminerlisation.

In situ effect of Tooth Mousse containing CPP-ACP on human enamel subjected to in vivo acid attacks

OBJECTIVE

This in situ study aimed to evaluate the protective effect of Tooth Mousse (GC) containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on human enamel erosion and to compare the difference in erosion between the anteriorly and posteriorly positioned human enamel.

METHODS

This study used a 2-treatment (7 days each) crossover design with 12 healthy volunteers wearing intraoral appliances. Each appliance contained 4 human enamel specimens positioned on the buccal surfaces of the volunteers' maxillary central incisors and first molars. The specimens were intraorally treated withTooth Mousse (CPP-ACP group) or deionized water (control group) for 3 min and then exposed to in vivo acid attacks by rinsing with 150 ml of a cola drink (4 × 5 min/day). The surface microhardness (SMH) of the specimens was measured and used to calculate the percentage of SMH loss (%SMH_l). Erosion effect on enamel was also investigated by scanning electron microscopy (n = 4) at the end of study. The data were statistically analysed using two-way analysis of variance (ANOVA) and Tukey's test at a level of P < 0.05.

RESULTS

A significant decrease in %SMH_l was observed for the specimens of CPP-ACP group compared to that for the controls (P = 0.007). The specimens positioned posteriorly exhibited a significantly lower %SMH_l than those positioned anteriorly (P = 0.033). Samples of CPP-ACP group showed fewer etching patterns than those of the control group.

CONCLUSIONS

In this in situ model, application of Tooth Mousse containing CPP-ACP before erosion reduced the %SMH_l of human enamel. Enamel located in different positions showed different patterns of erosion.

CLINICAL SIGNIFICANCE

Application of Tooth Mousse containing CPP-ACP could be considered as a suitable preventive strategy against enamel erosion. ClinicalTrials.gov Identifier: NCT03426150.

TiF4 gel effects on tubular occlusion of eroded/abraded human dentin

This in situ study evaluated the tubular occlusion caused by 4% TiF₄ gel on the surface of eroded/abraded dentin. Sixty human dentin samples were eroded in vitro and assigned into six groups (n = 10) according to the in situ surface treatment and number of cycling days: 4% TiF₄ gel applied once (TiF₄ 1), twice (TiF₄ 2), or three times (TiF₄ 3) followed by 2, 4, and 6 days of erosive/abrasive in situ cycling, respectively. Control groups (no treatment) were subjected to 2 (C1), 4 (C2), and 6 (C3) days of erosive/abrasive in situ cycling only. A seventh group (n = 10) was comprised by in vitro uneroded samples (UN), subjected to 6 days of in situ erosive/abrasive cycling. Each cycling day consisted on six erosive (0.5% citric acid, pH 2.6) and one abrasive events. Environmental scanning electron microscopy micrographs were taken. For all groups, blinded examiners assessed dentin tubules occlusion using visual scores (0-unoccluded, 1-partially occluded by granular deposits, 2-partially occluded by reduction in tubular lumen into diamond shape, 3-completely occluded) on images captured prior and after the in situ phase. Scheirer-Ray-Hare test demonstrated that treatments significantly affected tubule occlusion (p < .001). Dunn's test showed that tubule occlusion in TiF₄ 3 was significantly higher than in C1. Tubule occlusion in remaining groups did not differ from that observed in groups TiF₄ 3 and C1. Tubule occlusion was significantly higher after in situ phase. It may be suggested that TiF₄ , when applied three times, was able to positively change tubule occlusion of dentin samples.

In situ effect of CPP-ACP chewing gum upon erosive enamel loss

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is able to increase salivary calcium and phosphate levels at an acidic pH. Previous studies demonstrated that a CPP-ACP chewing gum was able to enhance the re-hardening of erosion lesions, but could not diminish enamel hardness loss. Therefore, there is no consensus regarding the effectiveness of CPP-ACP on dental erosion.

Is It Necessary to Prepare the Enamel before Dental Bleaching?

The aim of this in vitro study was to assess the influence of distinct surface treatments on the microhardness and color of enamel that will be bleached. Surface treatments are tested, accordingly: G1, no treatment; G2, 2% sodium fluoride; G3, casein phosphopeptide paste; G4, 2% fluoride+Nd:YAG laser. Forty blocks from bovine teeth composed the sample that were tested in Knoop microhardness (n = 10) and in color change (n = 10). After 24 h, bleaching with 35% hydrogen peroxide was performed for 45 min. Microhardness and color changes (using parameters ΔE, ΔL, Δa, and Δb) were assessed before and after bleaching. The data were analyzed by two-way ANOVA and Tukey's test (p < 0.05). Despite all surface treatments, a reduction of enamel microhardness occurred immediately after bleaching in all groups, being greater in G1. Enamel color changed in all groups. Immediately after bleaching, there was a decrease on enamel microhardness. However, after 7 days, some of those specimens previously treated before bleaching significantly recovered their initial microhardness without influencing the esthetic results of bleaching.

Effect of different salivary exposure times on the rehardening of acid-softened enamel

This in situ study assessed the effect of different times of salivary exposure on the rehardening of acid-softened enamel. Bovine enamel blocks were subjected in vitro to a short-term acidic exposure by immersion in 0.05 M (pH 2.5) citric acid for 30 s, resulting in surface softening. Then, 40 selected eroded enamel blocks were randomly assigned to 10 volunteers. Intraoral palatal appliances containing 4 enamel blocks were constructed for each volunteer, who wore the appliance for 12 nonconsecutive hours: initial 30 min, followed by an additional 30, and then by an additional 1 hour. For the last additional 10 hours the appliances were used at night, during the volunteers' sleep. Surface hardness was analyzed in the same blocks at baseline, after erosion and after each period of salivary exposure, enabling percentage of surface hardness recovery calculation (%SHR). The data were tested using repeated measures ANOVA and Tukey's test (α = 0.05). Increasing periods of salivary action promoted a progressive increase in the surface hardness (p < 0.001). However a similar degree of enamel rehardening (p = 0.641) was observed between 2 hours (49.9%) and 12 hours (53.3%) of salivary exposure. Two hours of salivary exposure seems to be appropriate for partial rehardening of the softened enamel surface. The use of the intraoral appliance during sleep did not improve the enamel rehardening after erosion.

Influence of Calcium Phosphate and Apatite Containing Products on Enamel Erosion

For the purpose of erosion prevention the present study aimed to compare the efficacy of two biomimetic products and a fluoride solution to optimize the protective properties of the pellicle. After 1 min of in situ pellicle formation on bovine enamel slabs, 8 subjects adopted CPP-ACP (GC Tooth Mousse), a mouthwash with hydroxyapatite microclusters (Biorepair), or a fluoride based mouthwash (elmex Kariesschutz) for 1 min each. Afterwards, samples were exposed in the oral cavity for 28 min. Native enamel slabs and slabs exposed to the oral cavity for 30 min without any rinse served as controls. After oral exposure, slabs were incubated in HCl (pH values 2, 2.3, and 3) for 120 s and kinetics of calcium and phosphate release were measured photometrically; representative samples were evaluated by SEM and TEM. The physiological pellicle reduced demineralization at all pH values; the protective effect was enhanced by fluoride. The biomimetic materials also reduced ion release but their effect was less pronounced. SEM indicated no layer formation after use of the different products. However, TEM confirmed the potential accumulation of mineral components at the pellicle surface. The tested products improve the protective properties of the in situ pellicle but not as effectively as fluorides.

In situ Effect of Chewing Gum with and without CPP-ACP on Enamel Surface Hardness Subsequent to ex vivo Acid Challenge

The erosion-protective effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is controversial. This study aimed to investigate the ability of CPP-ACP chewing gum to prevent a single event of erosive demineralization in situ. Bovine enamel blocks (n = 120) were randomly assigned to 3 phases according to the baseline surface hardness: phase I (PI) - chewing gum with CPP-ACP, phase II (PII) - chewing gum without CPP-ACP, and control phase (PIII) - salivary effect without stimulation (no gum). Nineteen volunteers participated in this study during 3 crossover phases of 2 h. In PI and PII, the volunteers wore intraoral palatal appliances for 120 min and chewed a unit of the corresponding chewing gum for the final 30 min. In the control phase the volunteers wore the appliance for 2 h, without chewing gum. Immediately after intraoral use, the appliances were extraorally immersed in a cola drink for 5 min to promote erosive demineralization. The percentage of surface hardness loss was calculated. The data were analyzed by ANOVA models and Tukey's test. Lower enamel hardness loss was found after the use of chewing gum with CPP-ACP (PI: 32.7%) and without CPP-ACP (PII: 33.5%) compared to the salivary effect without stimulation (PIII: 39.8%) (p < 0.05). There was no difference between PI and PII (p > 0.05). The results suggest that the use of chewing gum immediately before an erosive demineralization can diminish enamel hardness loss. However, the presence of CPP-ACP in the chewing gum cannot enhance this protective effect.

Artificial Saliva Formulations versus Human Saliva Pretreatment in Dental Erosion Experiments

The aim of this study was to evaluate the erosion-preventive effect of different artificial saliva formulations and human saliva in vitro compared to human saliva in situ. In the in vitro experiment, bovine enamel and dentin specimens were stored in artificial saliva (4 different formulations, each n = 20), deionized water (n = 20) or human saliva (n = 6 enamel and dentin specimens/volunteer) for 120 min. In the in situ experiment, each of the 6 enamel and dentin specimens was worn intraorally by 10 volunteers for 120 min. The specimens were then eroded (HCl, pH 2.6, 60 s). Half of the specimens were subjected to microhardness analysis (enamel) and the determination of calcium release into the acid (enamel and dentin), while the other half were again placed in the respective medium or worn intraorally, respectively, for 120 min before a second erosion was performed. Knoop microhardness of enamel and the calcium release of enamel and dentin into the acid were again determined. Statistical analysis was conducted by two-way repeated-measures ANOVA or two-way ANOVA (α = 0.05). Enamel microhardness was not significantly different between all test groups after the first and the second erosive challenge, respectively. Enamel calcium loss was significantly lower in situ compared to the in vitro experiment, where there was no significant difference between all test groups. Dentin calcium loss was significantly lower than deionized water only after the first and than all except one artificial saliva after the second erosion. Under the conditions of this experiment, the use of artificial saliva formulations and human saliva in vitro does not reflect the intraoral situation in dental erosion experiments adequately.

The Future of Fluorides and Other Protective Agents in Erosion Prevention

The effectiveness of fluoride in caries prevention has been convincingly proven. In recent years, researchers have investigated the preventive effects of different fluoride formulations on erosive tooth wear with positive results, but their action on caries and erosion prevention must be based on different requirements, because there is no sheltered area in the erosive process as there is in the subsurface carious lesions. Thus, any protective mechanism from fluoride concerning erosion is limited to the surface or the near surface layer of enamel. However, reports on other protective agents show superior preventive results. The mechanism of action of tin-containing products is related to tin deposition onto the tooth surface, as well as the incorporation of tin into the near-surface layer of enamel. These tin-rich deposits are less susceptible to dissolution and may result in enhanced protection of the underlying tooth. Titanium tetrafluoride forms a protective layer on the tooth surface. It is believed that this layer is made up of hydrated hydrogen titanium phosphate. Products containing phosphates and/or proteins may adsorb either to the pellicle, rendering it more protective against demineralization, or directly to the dental hard tissue, probably competing with H+ at specific sites on the tooth surface. Other substances may further enhance precipitation of calcium phosphates on the enamel surface, protecting it from additional acid impacts. Hence, the future of fluoride alone in erosion prevention looks grim, but the combination of fluoride with protective agents, such as polyvalent metal ions and some polymers, has much brighter prospects.

In situ effect of a commercial CPP-ACP chewing gum on the human enamel initial erosion

OBJECTIVE

This study evaluated the in situ rehardening effect of a commercial chewing gum containing casein phosphopeptide - amorphous calcium phosphate (CPP-ACP) on initial erosion lesions.

METHODS

Seventy-two human enamel blocks, after selection (initial surface hardness - SHi) and in vitro short-term acidic exposure (cola drink for 3 min - SHd) were randomly assigned to three groups. The factors under study were treatment (3 levels: GI chewing gum with CPP-ACP, GII chewing gum without CPP-ACP and GIII control group without gum) and intraoral period (2 levels: 2 and 24h). Twelve volunteers wore intraoral palatal devices for 24h in 3 crossover phases. On each phase, after 2h the surface hardness was assessed (SHf1) and the blocks were reinserted and the devices were used for additional 22 h (SHf2). In phases of GI and GII volunteers chewed the respective gum during 30 min, for 4 times with an interval of 4h. Percentage of surface hardness recovery (%SHR) was calculated after 2 and 24 h. The data were analysed by repeated measures ANOVA and Tukey's test.

RESULTS

Chewing gum with CPP-ACP (2h=50.0%<24h=95.9%) showed higher hardness recovery than chewing gum without CPP-ACP (2h=30.0%<24 h=71.1%) and control (2 h=15.7%<24 h=40.9%) (p<0.05).

CONCLUSIONS

The results suggest that saliva increased hardness of softened enamel after the use of conventional chewing gum (GII) and this effect was enhanced by the prolonged intraoral period (24 h) and by the use of CPP-ACP chewing gum (GI).

CLINICAL SIGNIFICANCE

Since chewing gum is an alternative to enhance salivary defenses after erosive challenges, CPP-ACP chewing gum might be a supplementary strategy to potentiate the mineral precipitation of initial erosion lesions.

Can demineralized enamel surfaces be bonded safely?

OBJECTIVE

To evaluate and compare the effects of enamel demineralization, microabrasion therapy and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application on the shear bond strength (SBS) of orthodontic brackets bonded to enamel surfaces and enamel color.

MATERIALS AND METHODS

Eighty freshly extracted human maxillary premolar teeth were allocated to one of the four groups. Brackets were bonded directly to non-demineralized enamel surfaces in Group I (control group), directly to the demineralized enamel surfaces in Group II, to demineralized enamel surfaces after CPP-ACP application in Group III and to demineralized enamel surfaces after microabrasion therapy in Group IV. The samples were stored in water for 24 h at 37°C and then underwent thermocycling. The SBS in megapascals (MPa) was determined by a shear test with 0.5 mm/min crosshead speed and failure types were classified with modified adhesive remnant index scores. The data were analyzed with one-way analyses of variance (ANOVA), Tukey and chi-square tests at the α = 0.05 level.

RESULTS

Significant differences were found among the four groups (F = 21.57, p < 0.01). No significant difference was found between Group I and III (17.12 ± 2.84 and 15.08 ± 3.42 MPa, respectively) or between Group III and IV (12.82 ± 2.64 MPa). The lowest SBS value was determined in Group II (5.88 ± 2.12 MPa). Enamel demineralization, microabrasion therapy and CPP-ACP application affected enamel color significantly.

CONCLUSION

CPP-ACP application and microabrasion therapy are able to increase the decreased SBS of orthodontic brackets because of enamel demineralization.

Durability of the anti-erosive effect of surfaces sealants under erosive abrasive conditions

OBJECTIVE

To test the durability of sealants applied for prevention of erosive dentine mineral loss under erosive/abrasive conditions.

METHODS

Forty-eight bovine dentine samples doped with (32)P were randomly allocated to four groups (1-4). All samples performed a de- and remineralizations pre-cycling (6 × 1 min erosion in HCl: pH 3.0, mean time and overnight immersion in artificial saliva) for 1 day. Sealing was done as follows; (1) unsealed, (2) Seal & Protect, (3) K-0184 (experimental sealer) and (4) OptiBond FL. After sealing, samples were immersed in HCl for 3 h (baseline measurement). Then, the following erosive/abrasive and remineralisations cycling was performed for 8 days: 3 h/day erosion with HCl, 600 brushing strokes/day and storage in artificial saliva for the rest of the day. Sealer permeability was evaluated by assignation of (32)P in the acid used for the erosive attacks.

RESULTS

At baseline, the significantly highest dentine loss was observed for the unsealed control group, while the mineral loss was not statistically significantly different between the sealed groups 2 and 3. At all days of the erosive/abrasive and remineralizations cycling and cumulatively the significantly highest mineral loss was observed for group 1, while the significantly lowest mineral loss was observed for the samples sealed with Seal & Protect (group 2) and K-0184 (group 3). In all groups, no significant increase in the (32)P release was observed.

CONCLUSION

Surface sealants are able to reduce the erosive dentine mineral loss and maintain this erosion-preventing efficacy over the whole duration (simulating 8 month in-vivo) of the erosive/abrasive cycling.

A Nanomechanical Investigation of Three Putative Anti-Erosion Agents: Remineralisation and Protection against Demineralisation

An increasing interest in dental erosion as a clinical and scientific phenomenon has led to concerted efforts to identify agents which might protect against erosion. In this study, nanoindentation was used to investigate inhibition of erosive enamel demineralisation over time scales with direct clinical relevance. Nanohardness of polished human enamel specimens (n = 8 per group) was measured at baseline (B), after demineralisation (D1: citric acid, 0.3% w/v, pH3.20, 20s), after treatment (T), and after a second demineralisation (D2: as above). Data were analysed using repeated measures ANOVA. All specimens exhibited a similar reduction in nanohardness B-D1 in the range 35.2-39.5%. The positive control solution (saturated hydroxyapatite solution) and 4500 mg/L fluoride as NaF significantly increased nanohardness D1-T by 19.9% and 24.1%, respectively, whereas 1400 mg/L fluoride as NaF, casein phosphopeptide-amorphous calcium phosphate mousse and negative control (deionised water) had no significant effect. Nanohardness at D2 was indistinguishable for all groups, with total reduction in nanohardness B-D2 of 31.6% (4500 mg/L fluoride), 35.2% (positive control), 39.9% (1400 mg/L fluoride), 42.4% (negative control), and 43.7% (CPP-ACP product). In summary, 4500 mg/L fluoride significantly increased the nanohardness of previously demineralised enamel and resulted in the smallest total reduction in nanohardness but there were few statistically significant differences among the groups.

Biofunctional properties of caseinophosphopeptides in the oral cavity

Caseinophosphopeptides (CPPs), bioactive peptides released from caseins, have the ability to enhance bivalent mineral solubility. This is relevant to numerous biological functions in the oral cavity (promotion of tooth enamel remineralisation, prevention of demineralisation and buffering of plaque pH). Therefore, CPPs may play a positive role as prophylactic agents for caries, enamel erosion and regression of white spot lesions. Most in vitro and in situ studies demonstrate strong evidence for the bioactivity of CPPs in the oral cavity. Nevertheless, relatively little is known concerning their use as adjuvants for oral health and more particularly regarding their long-term effects on oral health.